>
> I sent a patch about page allocation for less fragmentation.
> http://permalink.gmane.org/gmane.linux.kernel.mm/130599
>
> It proposes a page allocator allocates pages in the same pageblock
> for the drivers to move their unmovable pages. Some drivers which comsumes
> many pages
> and increases system fragmentation use the allocator to move their pages to
> decrease fragmentation.
>
> I think I can try another approach.
> There is a compaction code for balloon pages.
> But the compaction code cannot migrate pages of other drivers.
> If there is a generic migration framework applicable to any drivers,
> drivers can register their migration functions.
> And the compaction can migrate movable pages and also driver's pages.
>
> I'm not familiar with virtualization so I couldn't test this patch yet.
A RFC, no?
> But if mm developers agree with this approach, I will complete this patch.
>
> I would do appreciate any feedback.
>
> Signed-off-by: Gioh Kim <gioh....@lge.com>
> ---
> drivers/virtio/virtio_balloon.c | 2 ++
> include/linux/balloon_compaction.h | 23 +++++++++---
> include/linux/fs.h | 3 ++
> include/linux/pagemap.h | 26 ++++++++++++++
> mm/balloon_compaction.c | 68
> ++++++++++++++++++++++++++++++++++--
> mm/compaction.c | 7 ++--
> mm/migrate.c | 24 ++++++-------
> 7 files changed, 129 insertions(+), 24 deletions(-)
>
> diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
> index 0413157..cd9b8e4 100644
> --- a/drivers/virtio/virtio_balloon.c
> +++ b/drivers/virtio/virtio_balloon.c
> @@ -486,6 +486,8 @@ static int virtballoon_probe(struct virtio_device *vdev)
>
> balloon_devinfo_init(&vb->vb_dev_info);
> #ifdef CONFIG_BALLOON_COMPACTION
> + vb->vb_dev_info.mapping = balloon_mapping_alloc(&vb->vb_dev_info,
> + &balloon_aops);
> vb->vb_dev_info.migratepage = virtballoon_migratepage;
> #endif
>
> diff --git a/include/linux/balloon_compaction.h
> b/include/linux/balloon_compaction.h
> index 9b0a15d..0af32b3 100644
> --- a/include/linux/balloon_compaction.h
> +++ b/include/linux/balloon_compaction.h
> @@ -62,6 +62,7 @@ struct balloon_dev_info {
> struct list_head pages; /* Pages enqueued & handled to Host */
> int (*migratepage)(struct balloon_dev_info *, struct page *newpage,
> struct page *page, enum migrate_mode mode);
> + struct address_space *mapping;
Better if a comment line is added.
> };
>
> extern struct page *balloon_page_enqueue(struct balloon_dev_info
> *b_dev_info);
> @@ -76,10 +77,22 @@ static inline void balloon_devinfo_init(struct
> balloon_dev_info *balloon)
> }
>
> #ifdef CONFIG_BALLOON_COMPACTION
> -extern bool balloon_page_isolate(struct page *page);
> -extern void balloon_page_putback(struct page *page);
> -extern int balloon_page_migrate(struct page *newpage,
> - struct page *page, enum migrate_mode mode);
> +extern const struct address_space_operations balloon_aops;
> +extern int balloon_page_isolate(struct page *page);
> +extern int balloon_page_putback(struct page *page);
> +extern int balloon_page_migrate(struct address_space *mapping,
> + struct page *newpage,
> + struct page *page,
> + enum migrate_mode mode);
> +
> +extern struct address_space
> +*balloon_mapping_alloc(struct balloon_dev_info *b_dev_info,
> + const struct address_space_operations *a_ops);
> +
> +static inline void balloon_mapping_free(struct address_space
> *balloon_mapping)
> +{
> + kfree(balloon_mapping);
> +}
>
> /*
> * __is_movable_balloon_page - helper to perform @page PageBalloon tests
> @@ -123,6 +136,7 @@ static inline bool isolated_balloon_page(struct page
> *page)
> static inline void balloon_page_insert(struct balloon_dev_info *balloon,
> struct page *page)
> {
> + page->mapping = balloon->mapping;
> __SetPageBalloon(page);
> SetPagePrivate(page);
> set_page_private(page, (unsigned long)balloon);
> @@ -139,6 +153,7 @@ static inline void balloon_page_insert(struct
> balloon_dev_info *balloon,
> */
> static inline void balloon_page_delete(struct page *page)
> {
> + page->mapping = NULL;
> __ClearPageBalloon(page);
> set_page_private(page, 0);
> if (PagePrivate(page)) {
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index b4d71b5..de463b9 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -368,6 +368,9 @@ struct address_space_operations {
> */
> int (*migratepage) (struct address_space *,
> struct page *, struct page *, enum migrate_mode);
> + int (*isolatepage)(struct page *);
> + int (*putbackpage)(struct page *);
> +
> int (*launder_page) (struct page *);
> int (*is_partially_uptodate) (struct page *, unsigned long,
> unsigned long);
> diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
> index 4b3736f..715b5b2 100644
> --- a/include/linux/pagemap.h
> +++ b/include/linux/pagemap.h
> @@ -25,6 +25,7 @@ enum mapping_flags {
> AS_MM_ALL_LOCKS = __GFP_BITS_SHIFT + 2, /* under mm_take_all_locks() */
> AS_UNEVICTABLE = __GFP_BITS_SHIFT + 3, /* e.g., ramdisk, SHM_LOCK */
> AS_EXITING = __GFP_BITS_SHIFT + 4, /* final truncate in progress */
> + AS_MIGRATABLE = __GFP_BITS_SHIFT + 5,
> };
>
> static inline void mapping_set_error(struct address_space *mapping, int
> error)
> @@ -54,6 +55,31 @@ static inline int mapping_unevictable(struct address_space
> *mapping)
> return !!mapping;
> }
>
> +static inline void mapping_set_migratable(struct address_space *mapping)
> +{
> + set_bit(AS_MIGRATABLE, &mapping->flags);
> +}
> +
> +static inline void mapping_clear_migratable(struct address_space *mapping)
> +{
> + clear_bit(AS_MIGRATABLE, &mapping->flags);
> +}
> +
> +static inline int __mapping_ops(struct address_space *mapping)
> +{
> + return mapping->a_ops &&
> + mapping->a_ops->migratepage &&
> + mapping->a_ops->isolatepage &&
> + mapping->a_ops->putbackpage;
> +}
> +
> +static inline int mapping_migratable(struct address_space *mapping)
> +{
> + if (mapping && __mapping_ops(mapping))
s/__mapping_ops/__mapping_migratable/ given naming hurts brain?
> + return test_bit(AS_MIGRATABLE, &mapping->flags);
> + return !!mapping;
> +}
> +
> static inline void mapping_set_exiting(struct address_space *mapping)
> {
> set_bit(AS_EXITING, &mapping->flags);
> diff --git a/mm/balloon_compaction.c b/mm/balloon_compaction.c
> index fcad832..2e9d635 100644
> --- a/mm/balloon_compaction.c
> +++ b/mm/balloon_compaction.c
> @@ -131,8 +131,11 @@ static inline void __putback_balloon_page(struct page
> *page)
> }
>
> /* __isolate_lru_page() counterpart for a ballooned page */
> -bool balloon_page_isolate(struct page *page)
> +int balloon_page_isolate(struct page *page)
> {
> + if (!balloon_page_movable(page))
> + return false;
> +
> /*
> * Avoid burning cycles with pages that are yet under __free_pages(),
> * or just got freed under us.
> @@ -173,8 +176,11 @@ bool balloon_page_isolate(struct page *page)
> }
>
> /* putback_lru_page() counterpart for a ballooned page */
> -void balloon_page_putback(struct page *page)
> +int balloon_page_putback(struct page *page)
> {
> + if (!isolated_balloon_page(page))
> + return 0;
> +
> /*
> * 'lock_page()' stabilizes the page and prevents races against
> * concurrent isolation threads attempting to re-isolate it.
> @@ -190,15 +196,20 @@ void balloon_page_putback(struct page *page)
> dump_page(page, "not movable balloon page");
> }
> unlock_page(page);
> + return 0;
> }
>
> /* move_to_new_page() counterpart for a ballooned page */
> -int balloon_page_migrate(struct page *newpage,
> +int balloon_page_migrate(struct address_space *mapping,
> + struct page *newpage,
Looks the newly added mapping is not necessary, yes?
> struct page *page, enum migrate_mode mode)
> {
> struct balloon_dev_info *balloon = balloon_page_device(page);
> int rc = -EAGAIN;
>
> + if (!isolated_balloon_page(page))
> + return 0;
> +
> /*
> * Block others from accessing the 'newpage' when we get around to
> * establishing additional references. We should be the only one
> @@ -218,4 +229,55 @@ int balloon_page_migrate(struct page *newpage,
> unlock_page(newpage);
> return rc;
> }
> +
> +/* define the balloon_mapping->a_ops callback to allow balloon page
> migration */
> +const struct address_space_operations balloon_aops = {
> + .migratepage = balloon_page_migrate,
> + .isolatepage = balloon_page_isolate,
> + .putbackpage = balloon_page_putback,
> +};
> +EXPORT_SYMBOL_GPL(balloon_aops);
--
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